understanding-git/basics/git-states

#!/usr/bin/env bash

set -euo pipefail
scriptloc=$(cd $(dirname "${BASH_SOURCE[0]}") && pwd)

r() {
    cmd=$*
    echo "\$ $cmd"
    eval $cmd
    echo "------------"
}


tmpdir=$(mktemp -d)
pushd ${tmpdir}

# delete temporary directory on script exit
cleanup() {
    rm -rf "${tmpdir}"
}

trap cleanup EXIT

clear

# Initialise repository
r git init

git config --local user.name "Achilleas Koutsou"
git config --local user.email "ak@example.com"

r git status

echo ":: Status: Initialised; no commits; no files"
read
clear

# ADD README

echo "
# Demo repository

Repository for demonstrating git workflow and file state cycle
" > README.md

r git status
echo ":: Status: No commits; one *untracked* file"
read
clear

r git add README.md

r git status
echo ":: Status: No commits; one *tracked* file, *staged*"
read
clear

# Commit

r git commit -m '"Initial commit: Add README"'

r git status
echo ":: Status: Clean! One unmodified file (doesn't show up in status)"
read
clear

# EDIT README
echo "

© AK 2019
" >> README.md

r git status
echo ":: Status: README is modified"
read
clear

# STAGE README

git add -u  # -u stages all *tracked* *modified* files (stands for update); does not add untracked files

r git status
echo ":: Status: README is staged"
read
clear

# Create python file in source directory
mkdir src
echo "import sys


def main():
    args = sys.argv
    print(f'Script name {args[0]}')
    print('Arguments received')
    for idx, arg in enumerate(sys.agv):
        print(f'{idx}: {arg}')

if __name__ == "__main__":
    main()
" > src/script.py

r git status
echo ":: Status: A new file appears, so it's untracked"
echo ":: Since the entire 'src' directory is untracked, we only see the name of the directory"
read
clear

# ADD the script
git add src
r git status
echo ":: Status: Both files are staged"
read
clear

# Commit staged files
r git commit -m '"Add script.py and copyright year"'

r git status
echo ":: Status: Commit done; all is clean"
read
clear

# Moving backwards through states
echo "Just some notes, do not commit" > notes.txt
git add notes.txt

r git status
echo ":: Status: New staged file; added accidentally"
read
clear

# Unstage it
r git reset HEAD notes.txt

r git status
echo ":: Status: unstaged (back to untracked) using 'git reset HEAD'"
read
clear

# Let's try that with one of our tracked files
echo "Another note" > src/script.py

r git status
r cat src/script.py
echo ":: OH NO! We wiped our script"
read

r git checkout -- src/script.py
r git status
r cat src/script.py
echo ":: SAVED"
read
clear

# Let's do that again
echo "Note three" > src/script.py

r git add src
r git commit -m '"Commit: some notes"'

r git status
echo ":: All clean except untracked notes"
read

r cat src/script.py
echo ":: Oops, we overwrote our script (again) and committed it!"
read
clear

r git log
echo ":: git log: repository history"
read
clear

# Let's find out when this happened
r git log -- src/script.py
echo ":: History of specific file"
read
clear

# Can also show the actual changes
r git log -p -- src/script.py
echo ":: History with differences (-p: patch)"
read
clear

# Previous commit has our file in good condition
r git checkout HEAD~1 -- src/script.py
r cat src/script.py
r git status
echo ":: Status: checked out old version of file; the checkout also staged the change"

# Commit the correction
r git commit -m '"Get back good script.py"'
r git status
read
clear

r git log
read